Suppose n is a positive integer, and let a₁. a2.....an be real numbers such that a₁ < a2 < ….. < an. Let (-[infinity], a₁) denote the set {ï € IR ·x < a}. Obtain a formula for the set {r € RR : (x-a₁)(x-a2) · · · (x—an) < û} using the notation for intervals.